情景：
今天在Ubuntu 9.10 上装ccfinder，装完Ubuntu 9.10 时安装软件时显示
ppc@ubuntu:/etc/apt$ sudo apt-get install vim
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package vim is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package vim has no installation candidate
从网上搜了一下是源有问题，于是去搜ubuntu 9.10的源列表！（源列表）
发现Ubuntu 9.10的源已经停止维护了。
解决方法：
根据大神们的方法（参考链接），更改了源列表，然后成功update。
方法一：直接将链接2的源列表复制粘贴过来。（Ubuntu 9.10 可用的apt更新源）
deb http://old-releases.ubuntu.com/ubuntu/ karmic main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ karmic-security main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ karmic-updates main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ karmic-proposed main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ karmic-backports main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ karmic main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ karmic-security main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ karmic-updates main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ karmic-proposed main restricted universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ karmic-backports main restricted universe multiverse方法二：这个更适合其他不同版本的源列表更新，将 源列表网址部分替换为
http://old-releases.ubuntu.com/releases/
如
deb-src http://old-releases.ubuntu.com/ubuntu/ karmic-backports main restricted universe multiverse
还有一个条命令：lsb_release -a 查看当前版本代号。
参考网址：